When Mannerheim started his
military career in Russia, the Russian army comprised approximately 35,000 officers and
850,000 men. The strength of the cavalry was approximately 75,000 men, 99 regiments.

The men were enlisted on conscription; the officers were mainly recruited from military
and cadet schools, and quite many of them were of noble blood or from higher social
classes. In principle, the requirements for a post of a field officer were attendance at a
military school or service in the Guard. At the end of the 1800s there was such a throng
to the higher posts that it was considered necessary to set an upper age limit. For a
cavalry officer it was 56 years.

During the wars, the total strength of the army
increased, being 42,000 officers and 1,050,000 men in 1904, and 38,000 officers and
2,700,000 men in 1914.

During the Russo-Japanese war the number of cavalry divisions increased to 30; owing to
losses, the total strength was approximately 74,000. At the outbreak of the First World
War, the cavalry comprised 24 divisions and 8 brigades. It was organized into army corps,
and the number of regiments was increased, from cossacks in particular. At the time of the
October Revolution, the cavalry of the Russian army comprised 10 staffs of army corps, 47
divisions and 9 brigades.

The casualties in the world war were great and more men were recruited. At the
beginning of the revolution of 1917 (1 March), there were 128,000 officers and 7,007,000
men in the army. When Mannerheims career in Russia ended at the time of the October
Revolution, the strength of the acting troops, i.e. on the front, was approximately
6,350,000 men. Around 7,500,000 men had been killed, injured or captured during the war.

The discipline in the army slackened considerably during the revolutions, and a number
of officers were shot. The councils elected by the soldiers interfered in leading, which
made the warfare nearly impossible. After the October Revolution, the democratization
process of the army proceeded further: the commanders were elected by men, the officer
ranks were repealed and desertion increased. The Bolsheviks had persuaded the army to side
with them by promising peace and disbandment. The Russian army was gradually disbanded
during the period of time from December 1917 till March 1918.